FIG. 4.—

Reconstruction of the ancestral karyotypes of fugu–Tetraodon and pufferfishes–medaka. The proto-chromosomes of the pufferfishes–medaka (FTM ancestor) are labeled from A to X. Genome segments in each species are color coded according to the chromosome of the FTM ancestor. The length of chromosomes of extant species indicates the number of orthologs. Scale bar represents 20 orthologs. Gene order within chromosomes of each species has been reallocated to highlight orthologous relationships with gene on the FTM ancestral chromosomes. Major chromosomal fusions are indicated as solid arrows. Major translocations of the genome segments containing at least four orthologs are displayed as dotted arrows. FT ancestor means the common ancestor of fugu and Tetraodon. Details of orthologs are shown in supplementary table S3, Supplementary Material onine. ^aData of divergence times in phylogram are from Benton and Donoghue (2007).